/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.app;

// Need the following import to get access to the app resources, since this
// class is in a sub-package.

import com.example.android.apis.R;

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.widget.EditText;
import android.widget.TextView;

/**
 * Simple example of using persistent preferences to retain a screen's state.
 * <p>
 * This can be used as an alternative to the normal
 * <code>onSaveInstanceState()</code> mechanism, if you wish the state to
 * persist even after an activity is finished.
 * </p>
 * 
 * <p>
 * Note that using this approach requires more care, since you are sharing the
 * persistent state potentially across multiple instances of the activity. In
 * particular, if you allow a new instance of the activity to be launched
 * directly on top of the existing instance, the state can get out of sync
 * because the new instance is resumed before the old one is paused.
 * </p>
 * 
 * <p>
 * For any persistent state that is not simplistic, a content provider is often
 * a better choice.
 * </p>
 * 
 * <p>
 * In this example we are currently saving and restoring the state of the top
 * text editor, but not of the bottom text editor. You can see the difference by
 * editing the two text fields, then going back from the activity and starting
 * it again.
 * </p>
 * 
 * <h4>Demo</h4> App/Activity/Save &amp; Restore State
 * 
 * <h4>Source files</h4>
 * <table class="LinkTable">
 * <tr>
 * <td class="LinkColumn">src/com.example.android.apis/app/PersistentState.java</td>
 * <td class="DescrColumn">The Save/Restore Screen implementation</td>
 * </tr>
 * <tr>
 * <td class="LinkColumn">/res/any/layout/save_restore_state.xml</td>
 * <td class="DescrColumn">Defines contents of the screen</td>
 * </tr>
 * </table>
 * 
 */
public class PersistentState extends Activity {
	/**
	 * Initialization of the Activity after it is first created. Here we use
	 * {@link android.app.Activity#setContentView setContentView()} to set up
	 * the Activity's content, and retrieve the EditText widget whose state we
	 * will persistent.
	 */
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// Be sure to call the super class.
		super.onCreate(savedInstanceState);

		// See assets/res/any/layout/save_restore_state.xml for this
		// view layout definition, which is being set here as
		// the content of our screen.
		setContentView(R.layout.save_restore_state);

		// Set message to be appropriate for this screen.
		((TextView) findViewById(R.id.msg)).setText(R.string.persistent_msg);

		// Retrieve the EditText widget whose state we will save.
		mSaved = (EditText) findViewById(R.id.saved);
	}

	/**
	 * Upon being resumed we can retrieve the current state. This allows us to
	 * update the state if it was changed at any time while paused.
	 */
	@Override
	protected void onResume() {
		super.onResume();

		SharedPreferences prefs = getPreferences(0);
		String restoredText = prefs.getString("text", null);
		if (restoredText != null) {
			mSaved.setText(restoredText, TextView.BufferType.EDITABLE);

			int selectionStart = prefs.getInt("selection-start", -1);
			int selectionEnd = prefs.getInt("selection-end", -1);
			if (selectionStart != -1 && selectionEnd != -1) {
				mSaved.setSelection(selectionStart, selectionEnd);
			}
		}
	}

	/**
	 * Any time we are paused we need to save away the current state, so it will
	 * be restored correctly when we are resumed.
	 */
	@Override
	protected void onPause() {
		super.onPause();

		SharedPreferences.Editor editor = getPreferences(0).edit();
		editor.putString("text", mSaved.getText().toString());
		editor.putInt("selection-start", mSaved.getSelectionStart());
		editor.putInt("selection-end", mSaved.getSelectionEnd());
		editor.commit();
	}

	private EditText mSaved;
}
